1. Field of the Invention
This invention relates to a process for producing alpha olefins in a Fischer-Tropsch synthesis utilizing slurried Fe-Co catalyst system derived from the in situ decomposition of Fe and Co metal carbonyl complexes.
2. Brief Description of the Prior Art
Fischer-Tropsch processes using iron-based catalysts including cobalt as a co-catalyst, are known to produce gaseous and liquid hydrocarbons containing C.sub.2 -C.sub.4 olefins. Because of the importance of C.sub.2 -C.sub.4 olefins, particularly as feedstocks for the chemical industry, modifications of the Fischer-Tropsch process are constantly being pursued toward the goals of maximizing C.sub.2 -C.sub.4 olefin selectivity while maintaining high catalyst activity and stability under the reaction conditions. The main thrust of the efforts in this area has been in the area of new catalyst development.
Disclosures in the art directed to Fischer-Tropsch processes employing iron-cobalt catalysts and alloys and/or description of these general types of catalyst materials, include: U.S. Pat. No. 2,850,515; U.S. Pat. No. 2,686,195; U.S. Pat. No. 2,662,090; U.S. Pat. No. 2,735,862; AICHE 1981 Summer Nat'l Meeting Preprint No. 408, "The Synthesis of Light Hydrocarbons from CO and H.sub.2 Mixtures over Selected Metal Catalysts", ACS 173rd Symposium, Fuel Division, New Orleans, March 1977; J. Catalysis 1981, No. 72(1), pp. 37-50; Adv. Chem. Sec. 1981, 194, 573-88; Physics Reports (Section C of Physics Letters) 12 No. 5 (1974) pp. 335,374; UK Patent Application No. 2050859A; J. Catalysis 72, 95-110 (1981); Gmelins Handbuch der Anorganische Chemie 8, Auflage (1959), pp. 59; Hydrocarbon Process, pp. 81-96 (May 1983); Chem-Ing.-Tech. 49 (1977) Nr. 6, pp. 463-468; and U.S. Pat. No. 4,154,751.
In this technology, it is also known that high levels of cobalt in an iron-cobalt alloy can produce enhanced selectivity to paraffinic products, as described in Stud. Surf. Sci. Catal. 7, Pt A, pp. 432 (1981).
The reference J.C.S. Chem. Comm. p. 428-430 (1983) describes complexes such as HFeCo.sub.3 (CO).sub.12 which can effectively be supported on basic supports such as silica modified by amino donor functions. The complexes are described as yielding active FischerTropsch catalysts giving rise to an unusual hydrocarbon product distribution.
A recent trend in the development of Fisher-Tropsch synthesis of alpha olefins has been in the area of slurry catalysis as opposed to fixed bed catalysts synthesis. An advantage of the slurry process is that better control of heat dissipation and catalyst maintenance can be achieved. Particularly what is being sought is a technique for preparing the slurry catalyst, which must be finely divided for good catalyst activity, in situ in the slurry liquid, as opposed to the ex situ preparation which is generally practiced in the art as described in the above reference.